1. Field of Invention
This invention relates generally to the field of control systems. More particularly this invention relates to control systems using data link modules communicating on a serial time-division multiplex bus capable of transferring large amounts of complex data.
2. Description of the Related Art
Serial multiplexed data systems, or bit level networks, capable of communicating single bit and variable length words, are well known as described in U.S. Pat. No. 4,808,994, issued on Feb. 28, 1989, and U.S. Pat. No. 5,706,289 issued on Jan. 6, 1998, both to Robert E. Riley, incorporated herein by reference.
The previous systems have benefits that include low cost, the use of only four wires for power and communication, and efficient data transfer. However, these bit level networks have traditionally been limited to transferring discrete input and output status data and some limited analog values. In the bit level networks of the prior art, data is transmitted in a unit termed a scan. A scan consists of a data frame for each available data channel prefaced by a synchronizing signal.
The data frame generally consists of a predetermined number of bits, typically 512 bits, which contains commands and data positioned within the data frame to coincide with the frame address boundaries configured in the modules. After receiving the synchronizing signal, each module watches for the command/data located at the proper position of the proper channel corresponding to the frame address and channel number configured for that module.
Often it is desirable to transfer large amounts of complex data containing information about a remote piece of equipment back to a central control station. Examples of such desirable information includes, but is not limited to, vibration, temperature, motor current, and voltage waveform data. These bit level network systems described by Riley provide efficient transfer of binary data and word data but are not cabable of transferring large amounts of data to limited addressing capabilities.
Accordingly, there is a need for a system and method for transferring large amounts of complex data across a bit level network. Further, there is a need to retain the simplicity, cost effectiveness, and reliability of the prior art bit level network while accomplishing the transfer of large amounts of complex data.